Sign up to receive free email alerts when patent applications with chosen keywords are publishedSIGN UP

Abstract:

Devices and methods of the invention can be used in many industries,
including: utilities, agriculture, food, textile, pharmaceutical,
photovoltaic and semiconductor, medical devices, chemical and
petro-chemical, material science, and defense, where monitoring and/or
analysis of various properties of materials are desired.

Claims:

1. A resonance type impedance sensor which is a multicoil open-core or
air-core inductor, said sensor comprising at least two coils, one coil
being an excitation coil connectable to at least one alternating current
source with frequency sweep, another coil being a sensing coil
connectable to at least one data processing system, wherein upon
electrical connection to said current source, said excitation coil
propagates an energy to said sensing coil, which generates a probing
electromagnetic field, and wherein L C R parameters of said sensing coil
are capable of providing resonance conditions for measuring of object
under test impedance at predetermined frequency.

2. The sensor of claim 1, further comprising said at least one alternating
current source with frequency sweep electrically connected to said at
least one excitation coil.

3. The sensor of claim 2, further comprising said at least one data
processing system in communication with said at least one sensing coil,
wherein L C R parameters of said sensing coil provides resonance
conditions for measuring of object under test impedance at predetermined
frequency.

4. An impedance sensing system for non-contact and non-invasive measuring
and analyzing of targeted chemical and physical properties of gaseous,
fluid and solid objects comprising:(A) at least one resonance type
impedance sensor of claim 1;(B) at least one alternating current source
with frequency sweep electrically connected to said at least one
excitation coil;(C) said at least one data processing system in
communication with said at least one sensing coil, wherein L C R
parameters of said sensing coil provides resonance conditions for
measuring of object under test impedance at predetermined frequency;
and(D) a control system in communication with said alternating current
source and said data processing system.

5. The impedance sensing system of claim 4, further comprising a fixture
to provide object under test placement in close proximity to said
sensor(s), so that electromagnetic field induced by said sensing coil(s)
can penetrate into said object under test.

6. A method of measuring chemical and physical properties of an object by
a resonance type impedance sensor, said method comprising:(A) measuring
self-resonance frequency and amplitude of said sensor(s);(B) placing an
object under test comprising at least one analyte;(C) measuring resonant
frequency and amplitude of sensor in the presence of said object;(D)
calculating changes in amplitude and resonant frequency induced by
electromagnetic interaction between said sensor and object to determine
impedance of said object under test; and(E) matching said impedance with
predetermined calibration data to determine said chemical or physical
properties of said object under test.

7. The method of claim 6, wherein said sensor is the sensor of claim 1.

8. The sensor of claim 3, wherein said data processing system has high
impedance input.

9. The sensor of claim 8, wherein said impedance input is greater than 10
MΩ.

10. The sensor of claim 2, wherein said alternating current source has an
adjustable current output.

11. The sensor of claim 1, wherein said sensor is configured as a
cylindrical multicoil inductor.

12. The sensor of claim 11, wherein said cylindrical multicoil inductor
has a ferromagnetic open core.

13. The sensor of claim 12, wherein said ferromagnetic core is configured
as a half pot core.

14. The sensor of claim 12, wherein said cylindrical multicoil inductor
has an adjustable ferromagnetic core.

15. The sensor of claim 1, further comprising a support element, wherein
said coils are mounted on said support element.

16. The sensor of claim 15, wherein said multicoil inductor is planar.

17. The sensor of claim 15, wherein said support element is a PCB type or
flexible support element.

18. The sensor of claim 11, further comprising a support element said
coils configured as multicoil inductor being mounted on said support
element.

19. The sensor of claim 18, wherein said support element has low
coefficient of electrical permittivity.

20. The sensor of claim 19, wherein said support element comprises
fluorinated polymer in contact with said mounted multicoil inductor.

21. The sensor of claim 11, further comprising means for adjusting said
sensor's operating frequency.

22. The sensor of claim 21, wherein said means for adjusting are an
adjustable inter-turn step.

23. The sensing system of claim 4, further comprising a vessel for
containing of said gaseous, liquid or bulk material object under test.

24. The sensing system of claim 23, wherein said at least one sensor is
configured to encompass said vessel, said sensor being configured as a
cylindrical multicoil inductor.

25. The sensing system of claim 23, wherein said at least one sensor is
mounted on the external or internal wall of said vessel.

26. The sensing system of claim 24 or 25, which comprises a section of
pipe, said sensor(s) being installed on said section of pipe.

27. The sensing system of claim 24 or 25, further comprising at least one
bypass tubing or a group of channels, said sensor(s) being installed on
said at least one bypass tubing or a group of channels

29. The sensing system of claim 28, wherein said means for measuring
environmental conditions comprise at least one additional impedance
sensor.

30. The method of claim 7, further comprising monitoring of time-related
changes in impedance and correlating said chemical or physical properties
of said object under test to said time-related changes in impedance.

31. The sensor of claim 1, further comprising a phase detector in
communication with said alternating current source and said data
processing system.

32. The method of claim 6, further comprising providing the sensor of
claim 23, and measuring amplitude and phase shift at fixed frequency
which is near resonance frequency of said sensor.

33. The method of claim 7, further comprising applying additional external
influence(s) on said object under test to improve sensitivity of said
sensing system.

34. The method of claim 33, wherein said additional external influence(s)
is selected from the group consisting of UV, IR, magnetic field,
electrostatic field, and acoustics wave (ultra sound).

35. The sensor of claim 1, wherein said sensing coil and said excitation
coil are spatially separated from one another.

[0004]This invention relates to a new extremely sensitive kind of
electrical sensors that makes possible measurement of physical
characteristics, detection and quantification of constituencies of
solids, bulk materials and fluids. More particularly, the new sensor
technology allows for new real-time non-contact methods for measurement,
detection and quantification of components in said materials regardless
of its conductivity, transparency and reflectivity under most
environmental condition to apply Impedance Resonance Spectroscopy.

SHORT DESCRIPTION OF THE INVENTION

[0005]An electrical resonance sensor that can be used in array of similar
by design sensors, where each sensor comprises two coils, one of which is
excitation coil and the other is sensing coil and in electromagnetic
coupling with object under test works at predetermined resonant frequency
that was chosen for providing strong correlation of sensor indication
with a parameter of interest in radiofrequency range (RF); and the method
of using said sensors to measure the physical characteristics and/or
composition of the subject under test without contact in real-time.

BACKGROUND

[0006]Human society is in continuous search for inexpensive versatile
technology that can in real-time without contact monitor numerous
technological process, environment, food production, public safety and
medical procedures. For example: semiconductor and photovoltaic
industries need an advanced process monitoring devices during entire
fabrication of Integrated Circuits (IC), flat panel displays and solar
panels. Starting from measuring properties of bare wafers and other
substrates, monitoring film thickness during various deposition and
polishing processes as well as final IC testing requires constant process
monitoring and measurements. Agriculture, food, chemical and
pharmaceutical industries are interested in sensing technology to monitor
different physical characteristics of organic and inorganic materials,
liquids and compositions of numerous constituencies within natural
limits. This invention is about a new extremely sensitive sensor system
that is a core for new measuring method that is applicable to broad range
of conductive, semiconductive and dielectric materials.

SUMMARY

[0007]In one aspect, the invention provides a resonance type impedance
sensor which is a multicoil open-core or air-core inductor, the sensor
comprising at least two coils, one coil being an excitation coil
connectable to at least one alternating current source with frequency
sweep, another coil being a sensing coil connectable to at least one data
processing system, wherein upon electrical connection to said current
source, the excitation coil propagates an energy to the sensing coil,
which generates a probing electromagnetic field and wherein L C R
parameters of the sensing coil are capable of providing resonance
conditions for measuring of object under test impedance at predetermined
frequency. Various embodiments and variants are provided and
contemplated.

[0008]In another aspect, the invention provides an impedance sensing
system for non-contact and non-invasive measuring and analyzing of
targeted chemical and physical properties of gaseous, fluid and solid
objects comprising: (A) at least one resonance type impedance sensor
described above; (B) at least one alternating current source with
frequency sweep electrically connected to said at least one excitation
coil; (C) said at least one data processing system in communication with
said at least one sensing coil, wherein L C R parameters of said sensing
coil provides resonance conditions for measuring of object under test
impedance at predetermined frequency; and (D) a control system in
communication with said alternating current source and said data
processing system. Various embodiments and variants are provided.

[0009]In yet another aspect, the invention provides a method of measuring
chemical and physical properties of an object by a resonance type
impedance sensor, the method comprising:

[0010](A) measuring self-resonance frequency and amplitude of said
sensor(s);

[0011](B) placing an object under test comprising at least one analyte;

[0012](C) measuring resonant frequency and amplitude of sensor in the
presence of said object;

[0013](D) calculating changes in amplitude and resonant frequency induced
by electromagnetic interaction between said sensor and object to
determine impedance of said object under test; and

[0014](E) matching said impedance with predetermined calibration data to
determine said chemical or physical properties of said object under test.
The preferred impedance sensor is the sensor described in the sensor
aspect of the invention.

[0015]It is often required nondestructive contactless in-situ measurements
and/or control of various multi-compositional fluids (e.g. water, blood,
slurries, different solvents, etc.) and its monitoring for metallic,
organic and nonorganic contamination. It is a very common task for many
technological processes in many industries including: chemical,
semiconductor, pharmaceutical, medicine, agriculture, food processing,
etc. Proposed systems and methods are able to detect very small changes
not only in mono-compositional structures and fluids but also in most of
multi-composition materials, multi-layers structure and liquids with
dissolved and/or homogenized constituencies.

[0016]The present invention is directed to sensing system (apparatus)
comprising of one or an array (cluster) of impedance type sensor(s) which
is able to create a non-contact probing, primarily by harmonic high
frequency electromagnetic fields in an object under test and analyze
complex object response to the sensor's probing field.

[0018]In particular, this invention discloses a structure of novel RF
impedance sensing system and sensors for contact-less real-time (in-situ)
measurements (analysis) of composition different materials including of
thin and thick films and layers during numerous production processes
(e.g. PVD, CVD, ECD, CMP, etc.) in Semiconductor, Flat Panel,
Photovoltaic and Disk Drive industries, material science, etc. Also,
present invention describes a new method and device (apparatus) for
testing liquids, solvents and gas analysis in chemical, food processing,
Agricultural and other industry fields as well as in testing
laboratories.

[0019]The sensing system is, actually, scanning an object under test by
generating sweeping voltages in the vicinity of pre-selected frequencies.
To provide maximum sensitivity and resolution each Impedance sensor is
designed to have resonance in presence of the object under test at one of
said pre-selected frequencies.

[0020]The Impedance sensors are able to monitor number of targeted
parameters (characteristic or properties) of the object by measuring
object response to the sensor's electromagnetic field variation
represented by resonance amplitude (value) change--dV, resonance
frequency shift--dFr and in some cases phase angle displacements--d φ
at pre-selected set of frequencies.

[0021]Data processing unit is able to compare and analyze statistically
filtered reaction of object-sensor complex on Impedance sensor outputs
(V, dV, and Fr, dFr and φ, dφ). The data processing unit stores
in memory reference data and an algorithm of their usage. The reference
data are acquired in process (usually named calibration) of measuring
similar objects with known properties. The algorithm correlates the
sensor output signals with quantified characteristic(s) of the targeted
property and can comprise interpolation, solution of a system of
equation, search in lookup tables and etc.

[0022]According to present invention the in-situ Impedance sensors may be
designed as an air core cylindrical or planar inductors in one group of
embodiments and as ferrite core inductors according to an another one.
Each of these sensors has at least one winding named as an excitation
coil and at least one winding named as a sensing coil. The excitation
coil is connected (coupled) to an output of RF sweep generator and
provides electromagnetic pumping to resonance circuit represented by
sensing coil. The sensing coil is generating probing electromagnetic
field, perceiving an influence on said field by object under test and
transferring information about the influence to multi-channel measuring
and data processing (signal analyzing) system.

[0023]The Impedance sensors, RF sweep generator and data processing system
are designed to function as a high speed closed loop self-tuning system
continuously searching for a resonance frequency of a system (unity)
sensor-object complex, calculating and presenting targeted parameters and
characteristics of the object in-real time (on-line) mode.

[0024]The present invention is believed to have an advantage of high
sensitive impedance measurements using electrical resonance circuit and
advantage of Electrochemical Impedance Spectroscopy and Dielectric
Relaxation Spectroscopy which provide method of defining optimal
operating frequencies for impedance measurements.

[0025]High sensitivity impedance measurements are achieved by using
refined resonance circuit composed of coil only. Target parameters of
impedance measurements are active capacitance and capacitive reactance of
object under test, so highest sensitivity can be achieved by minimizing,
as much as possible, self resistance and self capacitance of sensing
coil. Another improvement is using of excitation coil for transferring
energy to sensing coil by excluding generator source's impedance
influence on sensing resonance circuit.

[0026]State of the art assumes using plurality of frequencies for
determining chemical and/or physical properties by measuring electrical
impedance properties of an object, but nobody mentioned how the
frequencies are chosen. The present invention discloses a new advanced
approach. To determine an operating frequency for each impedance sensor
of the sensing system an impedance spectrometer is used.

[0027]The procedure for constructing of composition sensing system is
described below: [0028]A) preparing a set of samples with known
composition of target constituents that cover possible variations of
object under test; [0029]B) determining an electrical impedance spectrum
for each of said samples by scanning over a wide frequency range;
[0030]C) analyzing of said spectra to find set of frequencies, at which
difference between said spectra correlates with change of target
constituents portion and said constituents contribute to impedance with
different proportion, wherein number of selected frequencies should be at
least equal to number of explored constituents; [0031]D) constructing a
set of sensors with operating frequencies based on the results of step C;
[0032]E) assembling said set of sensors in proximity to object under
test; [0033]F) collecting and storing calibration data using set of
samples prepared at the step A; and [0034]G) elaborating and implementing
a data processing algorithm.

[0035]The above described improvements allowed constructing novel
measuring sensor with highest possible sensitivity in RF. The FIGS. 17
and 23 illustrate sensitivity scale of traditional and proposed methods.
The proposed sensor system and measurement method increased significantly
sensitivity over all known electrical methods. The improvement in
sensitivity level is different from a case to case dependant on
application. For some applications sensitivity improvement could be
measured by factors not percentages.

BRIEF DESCRIPTION OF THE DRAWINGS

[0036]This invention is described with reference to specific embodiments
thereof. These and other features and advantages of the present invention
will be apparent to those skilled in the art from the following detailed
description of preferred embodiments and with the accompanying drawings,
in which.

[0037]FIG. 1 depicts a simplified equivalent circuit of an Impedance
sensor of this invention and object under test response.

[0038]FIG. 2 illustrates response of dielectric object under test to
vortex electric field for the object located outside of a sensor.

[0039]FIG. 3 illustrates response of dielectric object under test to
vortex electric field for the object located inside of a sensor.

[0040]FIG. 4 illustrates response of conductive object under test to
vortex electric field for the object located outside of a sensor.

[0041]FIG. 5 illustrates response of dielectric object under test to
linear electric field for the object located inside a sensor.

[0042]FIG. 6 depicts a sectional view of one embodiment of the impedance
sensor (cylindrical type) of the present invention.

[0043]FIG. 7 depicts a sectional view of another embodiment of the
impedance sensor (bobbin type) of the present invention.

[0044]FIG. 8 depicts another embodiment of the present invention for
testing flowing in the pipe liquid and comprising an array of Impedance
sensors having tree different frequencies.

[0045]FIG. 9 depicts a general view of another embodiment of the Impedance
sensors array of the present invention comprising two bypass sections
wherein properties of fluid under test may be monitored by several
different impedance sensors (the bypass section can be periodically empty
for calibration and correction for wall deposit).

[0046]FIG. 10 depicts a sectional view of another embodiment of the
impedance sensor (ferrite pot type) of the present invention for
measuring solid object.

[0047]FIG. 11 depicts a sectional view of another embodiment of the
impedance sensor (ferrite pot type) of the present invention for
measuring liquids and bulk materials.

[0048]FIG. 12 depicts an embodiment of non-contact sensor device of this
invention for measuring liquids and bulk materials with excitation and
sensing coils embracing object under test.

[0049]FIG. 13 depicts a general view of an embodiment of a planar sensor
of the present invention.

[0050]FIG. 14 depicts a block diagram of the sensing system according to
the present invention;

[0051]FIG. 15 depicts scope screen shot of output signals of an impedance
sensing system of the present invention for a bare silicon wafer and for
the same silicon wafer covered by 5000 Åthick aluminum film.

[0052]FIG. 16 depicts a graph illustrating test results of a sensing
system of the present invention for samples of distilled water and tap
water.

[0053]FIG. 17, FIG. 18, and FIG. 19, depict graphs illustrating test
results of a sensing system of the present invention for samples of
distilled water and water having different concentrations of sodium
chloride (NaCl) in the frequency range of 17-20 MHz.

[0054]FIG. 20 and FIG. 21 depicts graphs illustrating test results of
measurements with sensing system of this invention for silicon wafers
having different thicknesses of aluminum film.

[0055]FIG. 22 depicts a graph illustrating test results of a sensing
system of the present invention for measuring mercury contamination in
water.

[0056]FIG. 23 depicts a graph of amplitude/frequency response curves for
solutions of water containing different concentration NaCl in the
frequency range of 17-20 MHz for a sensor of this invention with a 20 pF
capacitor.

[0057]FIG. 24 depicts maxima of amplitude/frequency response curves as a
function of the concentration of NaCl in water for embodiments of this
invention having a 20 pF capacitor and for a sensor system without added
capacitance.

[0059]Other patents disclosed apparatus and methods to measure physical
and chemical characteristics and their distributions using
Electrochemical Impedance Spectroscopy (EIS) and Dielectric Relaxation
Spectroscopy (DRS). USPTO Patent Application 20090027070 discloses a dual
cell Electrochemical Impedance System (EIS) testing apparatus and method
for measuring coating integrity on various substrates. U.S. Pat. No.
4,433,286 discloses identification of materials using their complex
dielectric response. U.S. Pat. No. 7,514,938 discloses dielectric
relaxation spectroscopy apparatus and method of use, for non-invasive
determination of presence or concentration of an analyte in the sample.

[0060]There are numerous measuring techniques suggested for measuring
thickness, uniformity, composition and contamination of thin and thick
layers. Optical methods, like ellipsometry, are common in the
semiconductor industry. They are mostly used for measurements of
transparent layers. The X-ray technique is expensive, associated with
safety issues and has limited application in production lines.

[0061]Other methods include AC and DC point probes, capacitive sensors
(U.S. Pat. No. 7,332,902), inductive Eddy current technology (US patent
publications 200501566042 and 20090079424) and others are dependent on a
variety of factors that are difficult to control. Enhancements of
Inductive and RF Impedance analyzing methods are disclosed in several
patents (e.g., U.S. Pat. No. 6,593,738 and U.S. Pat. No. 6,891,380).
Electrically based methods either require electrical connections to the
measured thin layer that often affect the measured object or are
noncontact, and are slow and have a low sensitivity.

[0062]It is believed that the optical methods often cannot be reliably
used when measuring opaque or nontransparent layers and stacks of
transparent layers. Things are further complicated by optical properties
of the measured layers (the index of refraction, extinction coefficient,
etc.) and by the surface roughness of the measured and/or underlying
layers.

[0063]Furthermore, the techniques known in the art are unable to measure
thicknesses of targeted individual layer(s) inside composite multi-layer
objects with high accuracy. Most of those known techniques are limited by
one or a combination of shortcomings such as speed of measurement,
optical properties and material's conductivity. In addition, some of
these techniques are destructive and/or require a direct contact which is
highly undesirable.

[0065]While the present invention is not limited to any specific theory,
traditionally a sensitive resonance circuit is an electrical circuit
composed of at least two elements: inductor and capacitor electrically
connected to each other. In order to maximize sensitivity of resonance
circuit to electrical impedance of an object under test it was believed
to be necessary to minimize capacitance and resistance of the resonance
circuit. The inventors have unexpectedly discovered that the traditional
electrical circuit, composed of inductor and capacitor, may be replaced
by an inductor alone. The said inductor (induction coil) should be
coreless or an open core type to serve as sensing element. The sensing
coil is a main part of the inductor and its parameters define operating
frequency of invented sensor. Sensor's sensitivity can be further
increased by using monolayer coil with substantial step between turns or
using basket winding to decrease self capacitance of sensing coil.

[0066]While the invention is not limited to any specific theory, another
significant feature that is believed to have contributed to high
sensitivity of the invented sensor is an electrical separation of AC
current source from the sensing coil; it is in order to exclude or
minimize the influence of source impedance on the sensor's sensitivity.
That was achieved by using excitation coil for electromagnetically
transferring energy from source of AC current to sensing coil.

[0067]Another important aspect of our sensor design that was never
introduced in prior art is a requirement for high input impedance of the
data processing module. To achieve high sensor sensitivity the input
impedance should be extremely high (for example, our data acquisition
unit has 10 GΩ input resistance). Correctness of such requirement
can be proven by formula:

[0068]From above formula, it is obvious that energy dissipation is smaller
when higher input resistance is used. For example, when we are replacing
10 GΩ DAQ by standard oscilloscope (even with 10 MΩ
attenuator) a drastic sink in sensor sensitivity is observed.

[0069]There are several patents (U.S. Pat. No. 4,058,766, U.S. Pat. No.
4,433,286, U.S. Pat. No. 6,669,557, U.S. Pat. No. 7,219,024) mentioned
use a plurality of frequencies for determining different chemical and
physical features of different objects through the measuring electrical
impedance, but none of the patent described criteria for defining
frequencies in use. Present invention uses phenomenon of changing
impedance property with changing of frequency for searching optimal
operating frequencies for sensors of composition sensing systems.
Information about object's impedance at frequencies, found using
impedance spectroscopy, make it possible to built a system of invented
impedance sensors to determine composition of liquid solutions, gas
mixtures, solid composite objects, multilayer objects or for monitoring
changing in such object composition.

[0070]FIG. 1 depicts a simplified equivalent circuit of an Impedance
sensor of this invention and object under test response. Impedance sensor
is depicted with solid lines. It comprised of alternating current source
with frequency sweep 11, excitation coil 12, sensing coil 13, and data
processing system 14.

[0071]The excitation coil function is pumping the sensing coil with
electromagnetic energy and a separate a sensing resonance circuit from
impedance of alternating current source.

[0072]Sensitive resonance circuit of this invention consists of sensing
coil only and may be described by parameters of this coil: inductance,
inter-turn capacitance, and active resistance.

[0073]Impedance sensor design according to aspects of the present
invention provides a low capacitance value. It can be desirable to reduce
capacitance to the lowest possible practical value.

[0074]A sensing coil is coupled with high impedance (preferably in the
range of about 107 to about 1015Ω) input of data
processing system.

[0075]Analyze of the equivalent circuit of impedance sensor of present
invention shows that output current from sensing coil is usually very
small (in the range 10-6-10-14 A).

[0076]Response of object under test is depicted with dashed lines.
Reactions of the object can be represented by three equivalent electrical
circuits: 15, 16, and 17.

[0077]Alternating magnetic field of sensing coil generates vortex electric
field E and this field, in its turn, induces vortex currents of different
type.

[0078]If a sensing coil is positioned in close proximity to a dielectric
solid object, the equivalent circuit 15 consists of resulting parameters
L, R, and C. Impedance of circuit 15 reflects resistance to vortex
displacement currents generated by vortex electric field E and energy
dissipation occurs due to alternating dielectric polarization (FIG. 2).

[0079]The same resulting parameters reflect response generated by vortex
displacement currents in a tube filled by dielectric fluid. In this
embodiment, an object is depicted surrounded by a sensing coil (FIG. 3).

[0080]For conductive objects, both solid and fluid, the equivalent
electrical circuit 16 can have only two resulting parameters L and R.
These parameters consider resistance to both vortex conductive and ionic
current flows caused by vortex electric field E and energy dissipation
occurs due to eddy currents (FIG. 4).

[0081]Alternating linear electric field E of sensing coil also induces
linear currents of different type. Conductive and dielectric objects
create capacitive coupling of sensor and object and this relationship is
presented by equivalent electrical circuit 17. The impedance reflects an
object's resistance to linear conductive currents, displacement currents,
or ionic currents generated by a potential gradient in a sensing coil
(FIG. 5) or potential difference between coil and object under test (not
illustrated).

DESCRIPTION OF EMBODIMENTS

[0082]Referring now to FIG. 6, that shows a sectional view of one
embodiment of the present invention that can be bobbinless or may have a
support member 63 which is generally formed as a short tube made from
non-conductive material with minimum electrical permittivity
(ξ˜2) at high RF frequency, such as fluoropolymers. The support
member 63 should have thin walls to further minimize sensor capacitance.

[0083]The first (upper) section of the support member 63 carries an
excitation coil 61 which may have only one or few turns of relatively
thick copper wire. One terminal of the excitation coil is connected to
ground and second one to low impedance output of RF sweep generator (not
shown).

[0084]Second section of the support member carries a sensing coil 62. This
coil is wound by thinner copper wire than excitation coil. Also, the
distance between turns of this coil can be made variable, so the
capacitance and inductance of the coil can be mechanically tuned
(changed). In this way, the operating frequency of the impedance sensor
can be adjusted.

[0085]A first terminal of the sensing coil 62 is depicted close to
excitation coil 61 and is also connected to the ground. A second terminal
of sensing coil is coupled to a high impedance input of multi-channel
measuring and data processing system. An end part of the sensing coil 62
is positioned in close proximity to an object 64 under test, which may be
solid or fluid. Excitation and sensing coils are wound in opposite
directions, so as to obtain the same direction of magnetic field for both
coils during transfer energy from the excitation coil to the sensing coil
and to provide their electrical separation.

[0086]Depending on coils' diameter and number of sensing coil turns the
embodiment can have wide range of operating frequencies. The range can be
divided in two diapasons: a. operating frequencies <50 MGz that are
used for measuring conductive objects and b. operating frequencies 50
MHz-1 GHz that are used for measuring dielectric and semi conductive
objects.

[0087]An alternative support member design for Impedance sensor is shown
in FIG. 7. A "bobbin type" support member 73 makes it possible to provide
a higher number of turns in the sensing coil 72 and use thinner wire for
this coil. Excitation coil 71 has one turn only. The hole in the center
of the bobbin is designed for using this sensor with an optical
displacement (proximity) sensor 74 to control distance from the coil to
film 76 deposited on substrate 75.

[0088]There are many applications of present invention related to
thickness measurement of thin insulative, conductive and semi conductive
layers of wafer, flat panel displays, solar panels, etc. Distance (or
gap) between an impedance sensor and targeted layer in the object under
test is a critical factor in these cases.

[0089]FIG. 8 depicts a general view of another embodiment of the present
invention wherein an array comprising three impedance sensors 81-83
operating at different frequencies. The sensor array of this embodiment
is able to monitor at least three constituents in liquids of the interest
the same time.

[0090]The bobbin-type embodiment with coils of the impedance sensors are
installed on sections of pipe 84 carrying a liquid (gas or bulk material)
under test. The sensors can be positioned at distances one from other far
enough to avoid substantial mutual interference or cross-talk. Also,
sensors could operate alternatively. In some embodiments, the distance
can be at least equal to or more than the radius of a larger neighboring
bobbin.

[0091]Each of Impedance sensors in the array in this embodiment has its
own (individual) operating frequency specific for each targeted
constituent. The sensor array is connected to a controller of the
Impedance sensing system (not shown).

[0092]FIG. 9 depicts a sectional view of another embodiment of the present
invention wherein a sensor array monitoring flowing fluid (e.g. a liquid)
which has included therein constituents of interest. The fluid is flowing
through a large diameter dielectric pipe (e.g., 3'' or more) or
conductive pipe 97 of any diameter. The impedance sensors 93, 94, 95, and
96 are mounted on two smaller bypassing pipes, 91 and 92, (number of
bypasses could vary) whose diameters can be configured depending on the
application. Each of the sensors has its own resonance frequency specific
for each targeted constituent of interest.

[0093]This embodiment shows an advantage of using bypass tubes whose
diameters match to the optimum diameter of impedance sensor coils
(inductance/operating frequency) required for measuring targeted
constituent. Also, bypass tubes help by providing suitable distances
between sensors working in a close resonance frequency range. Cross-talk
and interaction between several impedance sensors can be minimized in
this embodiment.

[0094]The bypasses can incorporate open and close valves to allow periodic
maintenance including calibration and cleaning wall deposits.

[0095]FIG. 10 depicts a sectional view of another embodiment of the
present invention in which both excitation coil 101 and sensing coil 102
are placed inside of a ferrite half-pot 103. In this embodiment, an
impedance sensor may be positioned in close proximity to the object 104
under test (e.g., like a substrate with deposited metal layer 105). The
ferrite pot in this embodiment is open to the object and provides high
magnetic flux to the object under test.

[0096]In further embodiments, other shapes of the ferrite cores, such as
single "I", "C" or "U" or "E" shapes may be used depending on application
requirements. In any case, ferrite cores can increase sensitivity of an
impedance sensor, especially, working with conductive and low resistivity
objects.

[0097]FIG. 11 depicts a sectional view of another embodiment of the
present invention in which sensor is the same as on FIG. 10, but mounted
on the wall of vessel 114, which can contains liquid state or bulk
material object under test 115. The sensor comprises excitation coil 111
and sensing coil 112 are placed inside of a ferrite half-pot 113.

[0099]FIG. 13 depicts a general view of another embodiment of the present
invention wherein an impedance sensor is configured as two concentric
planar inductors. An inner inductor is a sensing coil with many turns
where one terminal 131 is grounded and a second terminal 132 can be
connected to the controller (not shown). An outer inductor can be an
excitation coil grounded from one side 131 and connected to an
alternating current source with frequency sweep at other side 133.

[0100]A planar impedance sensor can be made by lithography method with
both inductors deposited on solid rigid or flexible isolative substrate.
This sensor design has several advantages like small size, simple
mounting (attaching) to objects like pipe and low cost.

[0101]FIG. 14 depicts another embodiment of the present invention in which
an array of N impedance sensors is connected to a system controller. FIG.
14 depicts a simplified block diagram of a sensing system with controller
of this invention.

[0102]Excitation coils (not shown) of each impedance sensor are connected
to outputs of a required number of RF sweep generators (RFG). The sensing
coils of each sensor are connected to high impedance inputs of a
multi-channel data processing system (MDS) in the controller.

[0103]Both RFG and MDS are connected to a control system that manages
information exchanges, scanning, test--measuring presentation of results
and other functions. The control system may have several optional
correction sensors (e.g., those used to monitor ambient air and/or fluid
temperature, humidity, and the like). A controller also may have an
interface module to send and receive signals (information) from a higher
level tool controller, machine or production floor system.

[0104]Real time measurement results may be displayed by controller and/or
used as feedback signals for an automated closed loop tool or machine
control system. This way the targeted parameter(s) of an object under
test may be automatically controlled and maintained within
technologically required limits.

[0105]Voltage/current output of the RFG can be adjusted depending on
electrical and physical properties of the object under test. For example,
for measuring the thickness of a conductive metal film, higher excitation
coil current/voltage provides increased sensitivity and resolution of the
sensing system.

[0106]Data processing system can analyze information from RFG, sensors S1
to SN and the control system. The results define specific Resonance
Frequency Fro and voltage amplitude Uo for each "object-sensor" system.
Based upon this information and calibration algorithms the MDS
(Multichannel Data processing System) made conversion of values Fro and
Vo in measurement units of the targeted physical or chemical parameters
like film thickness, liquid constituencies concentration, layer
permittivity and so on. This conversion for two parameters may be
illustrated by next system of equations:

{ X × k 11 + Y × k 21 = Fro
X × k 12 + Y × k 22 = Uo
##EQU00001##

Where X is the first targeted parameter (like film thickness), Y is the
second parameter (like wafer bulk conductivity), k11 and k12 are
frequency weight coefficients, k21 and k22 are output voltage weight
coefficients.

[0107]The coefficients k11, k21, k12 and k22 are usually found by using a
calibration method and then can be retrieved from the MDS memory where
they are regularly stored. Calibration procedure comprises measurements
of reference samples having known values of targeted parameter(s) and
calculation statistically meaningful weight coefficients using acquired
data.

EXAMPLES

[0108]The following examples are intended to illustrate different
applications of this invention, and are not intended to limit the scope
of this invention. Persons of ordinary skill in the art can use the
disclosures and teachings of this application to produce alternative
embodiments without undue experimentation. Each of those embodiments is
considered to be part of this invention.

Example 1

Test on Bare Silicon Wafer and on the Same Wafer Covered by 5000 Å
Thick Aluminum Film

[0109]FIG. 15 depicts a scope screen shot of output signal 151 of an
impedance sensor over a range of frequencies 32 MHz to 43 MHz in presence
of bare silicon wafer. The resonant frequency is 33.8 MHz, the resonant
amplitude is 10067 mV. Line 152 is the amplitude frequency curve for the
same impedance sensor in presence of the same silicon wafer covered by
5000 Å thick aluminum film. In this case, the resonance frequency is
41 MHz and the resonant amplitude is 1673 mV. Comparison of lines 151 and
152 shows, that the resonance frequencies and particularly the voltage
amplitudes are very different. This example illustrates the high
sensitivity of the novel impedance sensing system according to present
invention.

Example 2

Test on Samples of Distilled and Tap Water

[0110]Test fixture for calibration and measurement variable concentration
of different constituencies in liquid (water as an example) shown in FIG.
14, where impedance sensor embraces small vessel-sampler, which is
preferably made from Teflon.

[0111]FIG. 16 depicts a graph of the test results at different conditions:
161--when there was no liquid in the sampler, 162--when the sampler was
filled with distilled water, and 163--when sampler was filled with tap
water. The distilled water compared with the empty sampler showed only
relatively small change in the output amplitude of the sensor. There was
larger shift in resonance frequency from 12.5 MHz for the empty vessel
compared to 11 MHz for distilled water. However, the tap water
drastically changed both amplitude and resonance frequency. This result
is understandable because resistively of distilled water at 25° C.
is about 18.2-40 MΩ-cm and tap water is usually below 0.1
MΩ-cm.

[0112]This Example demonstrates a very high sensitivity of the novel
impedance sensing system and indicates that even small contamination of a
liquid object can be detected and quantified.

Example 3

Measuring Different Concentrations of NaCl in Water

[0113]To determine proper working frequencies for solutions of sodium
chloride (NaCl) in water, preliminary studies were carried out by probing
the harmonic electromagnetic field over a wide range of working
frequencies: 20 MHz, 70 MHz, 370 MHz, and 480 MHz. Frequencies in
vicinity of 20 MHz showed the better results.

[0114]The frequencies in the range of 17 to 20 MHz were chosen for an
impedance sensor. In the next example, the amplitude-frequency response
was measured for different concentrations of NaCl. FIG. 17 depicts a
graph of results of these measurements. As can be seen from the graph of
the amplitude-frequency curve, solutions containing different
concentrations of NaCl are clearly distinguishable from each other.
Distilled water (filled diamonds) produced the highest amplitude at a
frequency of about 19.6 MHz, the lowest concentration of NaCl produced
amplitude less than that of distilled water, and with increasing
concentrations of NaCl, the amplitude decreased, and the frequency of the
maximum amplitude decreased until a concentration of 0.1% was achieved.
Also, clearly shown is the finding that a 1% solution of NaCl produced
amplitude greater than that observed for the next lower concentrations.
These results demonstrate the ability of the novel impedance sensing
system to measure a wide range of concentrations of liquid constituencies
with high resolution.

[0115]FIG. 18 depicts dependence of impedance sensor's resonant amplitude
when concentration of NaCl is measured. FIG. 19 depicts the same
dependence when NaCl concentration is represented in logarithmic scale.

Example 4

Measurement of Thickness of Thin Aluminum Films on Silicon Wafers

[0116]FIG. 20 presents tests results of aluminum film thickness
measurement (depicted in the Angstroms range). A sensing system used an
open core resonance sensor similar to shown in FIG. 7. Frequency range
was set from 34 MHz to 43 MHz. The start point in the plot corresponds to
a bare silicon wafer with no aluminum film.

[0117]FIG. 21 depicts the same results where aluminum film thickness is
represented in logarithmic scale.

Example 5

Measurements of Mercury in Water

[0118]One of the most dangerous contaminants in drinking water is mercury.
This contamination is highly topical even at very small concentrations.
Therefore, we carried out a series of experiments to measure mercury (Hg)
concentrations in water.

[0119]In one group of experiments, the frequency range was found at which
concentration of ions of mercury (Hg+) in distilled water make a
significant change in the amplitude-frequency characteristic. This
frequency defines L, C and R reference values for a coil design. The
measuring coil can be constructed per well known design rules with
consideration of the particular lay-out. Also, to achieve maximum
sensitivity, it can be desirable to maintain self-capacitance C at
minimum for the measuring circuit. The next experiments were conducted
with the above mentioned sensor.

[0120]FIG. 22 is a graph depicting amplitude-frequency characteristics
(AFC) for samples with different concentration of Hg+ in distilled water.
Test results clearly demonstrated the ability of an impedance sensing
system of this invention to measure Hg+ concentration in distilled water
at levels as low as 1 ppb (part per billion).

Example 6

Decreased Sensitivity of IRT-Sensor if Resonant Circuit Includes a
Capacitor

[0121]To confirm our conclusion from the above of the role of capacitance
of an impedance resonance device in modulating the amplitude-frequency
relationships of an embodiment of this invention, we carried out a series
of studies using solutions of NaCl, as described in Example 3, but in
which the resonant circuit of the device includes a capacitor.

[0122]FIG. 23 depicts a graph of amplitude frequency response (AFR) curves
obtained using an IRT-sensor which has approximately four times fewer
winds than the sensor in Example 3 and with the addition of a 20 pF
capacitor. Using this modified sensor with the added capacitor, we found,
quite expectedly, that the amplitude-frequency relationships for each of
the NaCl solutions were nearly identical, with a noted absence of change
in either the amplitude or the frequency at which the maximum amplitude
was observed.

[0123]FIG. 24 depicts maxima of Amplitude Frequency Response curve's for
sensors with and without the added capacitor. As it can be distinctly
seen, embodiments having added capacitors (open circles) have a
substantially narrower range of useful signals (resonant frequency and
amplitude variation) compared to sensors without added capacitors. In
contrast, according to theory, we found that impedance resonance sensor
systems without the added capacitance showed a very wide range of useful
signals.

[0124]This Example demonstrates that systems and methods of this invention
have substantially greater sensitivity than prior art sensing systems.
Therefore, use of systems and methods of this invention can provide those
responsible for maintaining products free of unwanted contamination.